Waterproofing glossary

Hydrostatic pressure - the pressure water in saturated soil exerts against your foundation. It is why sealers fail: a coating with pressure behind it blisters off. It is what drainage systems are designed to relieve.

Drain tile / weeping tile - perforated pipe laid in washed stone and wrapped in filter fabric, which collects water and carries it to a discharge point or sump. 'Tile' is a historic term; it is plastic pipe today. A footing drain is drain tile at the base of the foundation on the outside. An interior perimeter drain is the same idea inside, under the basement floor slab, priced at $40-$120 per linear foot (Fixr, 2026).

Sump pit and sump pump - the pit is the basin water collects in; the pump lifts it out through a discharge line. A check valve in that line stops discharged water flowing back into the pit. Installation typically runs $800-$2,000 (Fixr, 2026).

Dimple board - dimpled plastic sheeting that creates an air gap between soil and wall so water drains down to the footing drain instead of pressing on the wall. Membrane - a continuous sheet or liquid-applied waterproof skin on the exterior wall. Sodium bentonite - clay that swells on contact with water to self-seal, $2-$5 per square foot (Fixr, 2026).

Efflorescence - white crystalline mineral salt deposits left when water evaporates out of masonry. Evidence of water movement, not mold. Damp-proofing - a thin asphaltic coating that slows moisture vapor, common on older foundations, and not capable of holding back liquid water under pressure. Vapor barrier - sheeting that keeps wall moisture off finished surfaces, $1,500-$4,000 installed (Fixr, 2026). Grading - the slope of the ground away from the house; the code target is at least 6 inches of fall in the first 10 feet (2021 IRC R401.3).